Field of the Invention
The present invention relates to a method for molding a fiber-reinforced plastic member and a device for molding a fiber-reinforced plastic member.
Description of the Related Art
Being lightweight and excellent in mechanical strength, fiber-reinforced plastics (FRPs) are used for structural members of an aircraft and the like.
For example, a stringer reinforcing a skin of an aircraft is also formed of FRPs. The stringers are provided at intervals parallel to one another on the back surface of the skin. A molding jig called a mandrel is used for molding the stringer as shown in Japanese Patent Laid-Open No. 2007-8147.
A fiber base material is pressed by the mandrel against the skin or the mold, and a resin, which impregnates the fiber base material, is heated and cured through the mandrel. Thus, a molded article can be obtained.
In Japanese Patent Laid-Open No. 2007-8147, the mandrel is formed in a shape that follows the shape of the skin, or the mandrel divided into multiple pieces is used, in order to mold the stringer in close contact with the skin which has a varying thickness.
In view of the heating step the mandrel undergoes during molding, it is preferable that the FRP of the same material as the molded article, or Invar having as low a thermal expansion coefficient as the FRP, is used as the material of the mandrel, which, however, makes the mandrel expensive.
Therefore, it is desirable to use an inexpensive material such as aluminum, despite its higher thermal expansion coefficient compared with the FRP. However, even when the dimensions of the mandrel are set so as to match the dimensions of the molded article upon elongation of the mandrel, a large dimensional difference between the FRP and the mandrel at a normal temperature makes it difficult to contain the fiber base material inside the mandrel, so that a good positional accuracy and internal quality cannot be obtained.
In that case, by dividing the mandrel into multiple pieces in the longitudinal direction of the stringer and arranging these pieces with a gap between one another, the dimensional difference can be absorbed by the gaps.
However, if the mandrel is divided, the form accuracy of the molded article degrades due to the positional shift of the pieces.
Japanese Patent Laid-Open No. 2007-8147 does not describe how to secure the form accuracy of the stringer when the divided mandrel is used.
On the basis of the above problem, the present invention aims to provide a method for molding a fiber-reinforced plastic member, which can secure the form accuracy required for the molded article while allowing inexpensive production of a molding jig, and a device used for molding a fiber-reinforced plastic.